A long-wave infrared zoom lens

Abstract

The application discloses a long-wave infrared zoom lens, which comprises a front fixed group, a zoom group, a compensation group, a rear fixed group and a protective window in sequence from an object side to an image side along an optical axis; the front fixed group comprises a first lens, the zoom group comprises a second lens, the compensation group comprises a third lens, the rear fixed group comprises a fourth lens and a fifth lens, and the second lens and the third lens can reciprocate along the optical axis; and the focal length range of the long-wave infrared zoom lens is 20mm-100mm. The long-wave infrared zoom lens has the advantages of small weight and light volume, and the zooming and compensation are respectively realized by using single lenses, so that the optical axis stability in the zooming process can be well ensured, the adjusting mode is simple, the requirement on the lens structure is low, production and assembly are simple, lens precision is easy to ensure, tolerance analysis is easy, and mass production is easier to realize.

Description

Technical Field

[0001] This application belongs to the field of infrared optical technology, and specifically relates to a long-wave infrared zoom lens. Background Technology

[0002] Infrared systems offer significant advantages over traditional optics. For instance, they can search, identify, and track targets even in adverse weather conditions, leading to their widespread application in aerospace and military air defense. Currently, most infrared zoom lenses on the market employ six infrared elements. These lenses are generally large, heavy, and expensive, presenting numerous inconveniences in practical use. Summary of the Invention

[0003] Based on this, the present invention proposes a long-wave infrared zoom lens, the specific technical solution of which is as follows.

[0004] A long-wave infrared zoom lens comprises, sequentially from the object side to the image side, a front fixed group, a zoom group, a compensation group, and a rear fixed group along the optical axis; the front fixed group includes a first lens, the zoom group includes a second lens, the compensation group includes a third lens, and the rear fixed group includes a fourth lens and a fifth lens; both the second lens and the third lens are capable of reciprocating along the optical axis; the focal length range of the long-wave infrared zoom lens is 20mm-100mm.

[0005] Preferably, the first lens is a positive meniscus lens with its convex surface facing the object side, the second lens is a biconcave lens, the third lens is a biconvex lens, the fourth lens is a negative meniscus lens with its convex surface facing the image side, and the fifth lens is a positive meniscus lens with its convex surface facing the object side.

[0006] Preferably, the focal length of the first lens is 148.41155mm, the focal length of the second lens is -41.685426mm, the focal length of the third lens is 44.806719mm, the focal length of the fourth lens is -80.402764mm, and the focal length of the fifth lens is 36.681550mm.

[0007] Preferably, the center thickness of the first lens is 9.08 mm, the object side radius of curvature is 224.992 mm, and the image side radius of curvature is 440.408 mm. The second lens has a center thickness of 4.19 mm, an object-side radius of curvature of -284.241 mm, and an image-side radius of curvature of 226.360 mm. The third lens has a center thickness of 4.16 mm, an object-side radius of curvature of 226.042 mm, and an image-side radius of curvature of -328.232 mm. The fourth lens has a center thickness of 4 mm, an object-side radius of curvature of -36.512 mm, and an image-side radius of curvature of -46.549 mm. The fifth lens has a center thickness of 5.07 mm, an object-side radius of curvature of 55.832 mm, and an image-side radius of curvature of 105.452 mm.

[0008] Preferably, during zooming, the maximum displacement of the second lens is 52.7 mm, and the maximum displacement of the third lens is 24 mm.

[0009] Preferably, during zooming, the interval between the first lens and the second lens is 7.05622mm-59.72631mm, the interval between the second lens and the third lens is 5.98278mm-82.87384mm, the interval between the third lens and the fourth lens is 14.12166mm-38.34177mm, and the interval between the fourth lens and the fifth lens is 35.42mm.

[0010] Preferably, the first to fifth lenses are all made of germanium.

[0011] Preferably, the image-side surface of the second lens, the object-side surface of the third lens, the object-side surface of the fourth lens, and the image-side surface of the fifth lens are aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0012] Preferably, the object side of the first lens is coated with a DLC film, and the image side of the first lens and the object side and image side of the second to fifth lenses are coated with anti-reflection films.

[0013] Preferably, the long-wave infrared zoom lens has an F-number of 1.2, a total optical system length of 193mm, and a field of view range of 8°-40° to accommodate a detector with a resolution of 640×512 and a pixel size of 17μm.

[0014] The long-wave infrared zoom lens provided by this invention has the following technical effects: (1) The entire lens consists of 5 lenses, which is lighter and smaller than the infrared zoom lens with 6 lenses used in the prior art; (2) Zooming and compensation are performed using a single lens, specifically using the second lens 2 for zooming and the third lens 3 for compensation. Since the single lens is used for zooming, the optical axis stability during the zooming process can be well guaranteed, and the adjustment method is simple. (3) The fifth lens can be moved slightly back and forth to achieve focusing. On the one hand, the imaging distance of the entire lens can be from 2m to infinity, which solves the problem of lens imaging defocus. On the other hand, the slight movement of the fifth lens can compensate for the high and low temperatures of the lens usage environment, so that the lens usage temperature can cover -40℃ to 60℃, achieving two goals at once.

[0015] (4) The long-wave infrared zoom lens of the present invention can achieve zoom from 20mm to 100mm, and the image is clear and of excellent quality during the zoom process, with an average MTF of >0.3 across the entire field of view. Attached Figure Description

[0016] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0017] Figure 1 This is a schematic diagram of the structure of a long-wave infrared zoom lens provided in an embodiment of this application; Figure 2 An optical transfer function diagram of a long-wave infrared zoom lens with a focal length of 30mm, provided for an embodiment of this application; Figure 3 An optical transfer function diagram of a long-wave infrared zoom lens with a focal length of 60mm, provided for an embodiment of this application; Figure 4 The optical transfer function diagram of the long-wave infrared zoom lens with a focal length of 100mm provided in the embodiments of this application is shown.

[0018] Among them, 1. First lens, 2. Second lens, 3. Third lens, 4. Fourth lens, 5. Fifth lens, 6. Protective window. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the equipment or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0021] This embodiment provides a long-wave infrared zoom lens with a working wavelength of 8μm-12μm, a focal length of 20mm-100mm, an F-number of 1.2, a total optical system length of 193mm, a maximum aperture of 104mm, and a field of view range of 8°-40°. It can be adapted to detectors with a resolution of 640×512 and a pixel size of 17μm.

[0022] The long-wave infrared zoom lens in this example, such as Figure 1 As shown, along the optical axis from the object side to the image side, it includes a front fixed group, a zoom group, a compensation group, a rear fixed group, and a protective window. The front fixed group includes a first lens 1, the zoom group includes a second lens 2, the compensation group includes a third lens 3, and the rear fixed group includes a fourth lens 4 and a fifth lens 5. Both the second lens 2 and the third lens 3 can reciprocate along the optical axis.

[0023] Among them, the first lens 1 is a meniscus positive lens with its convex surface facing the object side, the second lens 2 is a biconcave lens, the third lens 3 is a biconvex lens, the fourth lens 4 is a meniscus negative lens with its convex surface facing the image side, and the fifth lens 5 is a meniscus positive lens with its convex surface facing the object side.

[0024] The parameters of the first lens 1 to the fifth lens 5 in this embodiment of the long-wave infrared zoom lens are shown in Table 1.

[0025] Table 1 Parameters of each lens The focal length of the first lens 1 is 148.41155mm, the focal length of the second lens 2 is -41.685426mm, the focal length of the third lens 3 is 44.806719mm, the focal length of the fourth lens 4 is -80.402764mm, and the focal length of the fifth lens 5 is 36.681550mm.

[0026] The center thickness of the first lens 1 is 9.08 mm, the radius of curvature of the object side is 224.992 mm, and the radius of curvature of the image side is 440.408 mm. The center thickness of the second lens 2 is 4.19 mm, the radius of curvature of the object side is -284.241 mm, and the radius of curvature of the image side is 226.360 mm. The center thickness of the third lens 3 is 4.16 mm, the radius of curvature of the object side is 226.042 mm, and the radius of curvature of the image side is -328.232 mm. The fourth lens 4 has a center thickness of 4mm, an object side radius of curvature of -36.512mm, and an image side radius of curvature of -46.549mm. The center thickness of the fifth lens 5 is 5.07 mm, the radius of curvature of the object side is 55.832 mm, and the radius of curvature of the image side is 105.452 mm.

[0027] In this embodiment, during the zoom process, the maximum displacement of the second lens 2 is 52.7mm, which is used to change the focal length of the lens, and the maximum displacement of the third lens 3 is 24mm, which is used for compensation of the zoom group.

[0028] During zooming, the interval between the first lens 1 and the second lens 2 is 7.05622mm-59.72631mm, the interval between the second lens 2 and the third lens 3 is 5.98278mm-82.87384mm, the interval between the third lens 3 and the fourth lens 4 is 14.12166mm-38.34177mm, and the interval between the fourth lens 4 and the fifth lens 5 is 35.42mm.

[0029] Preferably, in this embodiment, the materials of the first lens 1 to the fifth lens 5 are all germanium.

[0030] In this embodiment, the image-side surface S4 of the second lens 2, the object-side surface S5 of the third lens 3, the object-side surface S7 of the fourth lens 4, and the image-side surface S10 of the fifth lens 5 are aspherical surfaces and satisfy the aspherical surface formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

[0031] The data for each aspherical surface are shown in Table 2.

[0032] Table 2 Aspherical data of lenses Preferably, the object side S1 of the first lens 1 is coated with a DLC film, and the image side of the first lens 1, the object side of the second to fifth lenses, and the image side S2-S10 are coated with anti-reflection films.

[0033] Based on this, the long-wave infrared zoom lens provided in this embodiment has the following technical effects: (1) The entire lens consists of 5 lenses, which is lighter and smaller than the infrared zoom lens with 6 lenses used in the prior art; (2) Zooming and compensation are performed using a single lens, specifically using lens 2 for zooming and a third lens 3 for compensation. Since the single lens is used for zooming, the optical axis stability during the zooming process can be well guaranteed, and the adjustment method is simple. (3) The fifth lens 5 can be moved slightly back and forth to achieve focusing. On the one hand, the imaging distance of the entire lens can be in the range of 2m to infinity, which solves the problem of lens imaging defocus. On the other hand, the slight movement of the fifth lens 5 can compensate for the high and low temperatures of the lens usage environment, so that the lens usage temperature can cover -40℃ to 60℃, achieving two goals at once.

[0034] (4) Figure 2-4 The optical transfer function (OTF) graphs of the infrared zoom lens in this embodiment are shown at focal lengths of 30mm, 60mm, and 100mm. The long-wave infrared zoom lens in this embodiment can not only achieve zoom from 20mm to 100mm, but also produce clear images and excellent image quality during zooming, with an average MTF > 0.3 across the entire field of view.

[0035] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A long-wave infrared zoom lens, characterized in that, Along the optical axis from the object side to the image side, the lens consists of a front fixed group, a zoom group, a compensation group, and a rear fixed group. The front fixed group is composed of a first lens, the zoom group is composed of a second lens, the compensation group is composed of a third lens, and the rear fixed group is composed of a fourth and a fifth lens. Both the second and third lenses can reciprocate along the optical axis. The focal length range of the long-wave infrared zoom lens is 20mm-100mm. The first lens has a center thickness of 9.08 mm, an object-side radius of curvature of 224.992 mm, and an image-side radius of curvature of 440.408 mm. The second lens has a center thickness of 4.19 mm, an object-side radius of curvature of -284.241 mm, and an image-side radius of curvature of 226.360 mm. The third lens has a center thickness of 4.16 mm, an object-side radius of curvature of 226.042 mm, and an image-side radius of curvature of -328.232 mm. The fourth lens has a center thickness of 4 mm, an object-side radius of curvature of -36.512 mm, and an image-side radius of curvature of -46.549 mm. The fifth lens has a center thickness of 5.07 mm, an object-side radius of curvature of 55.832 mm, and an image-side radius of curvature of 105.452 mm.

2. The long-wave infrared zoom lens as described in claim 1, characterized in that, The first lens is a positive meniscus lens with its convex surface facing the object side, the second lens is a biconcave lens, the third lens is a biconvex lens, the fourth lens is a negative meniscus lens with its convex surface facing the image side, and the fifth lens is a positive meniscus lens with its convex surface facing the object side.

3. A long-wave infrared zoom lens as described in claim 2, characterized in that, The first lens has a focal length of 148.41155 mm, the second lens has a focal length of -41.685426 mm, the third lens has a focal length of 44.806719 mm, the fourth lens has a focal length of -80.402764 mm, and the fifth lens has a focal length of 36.681550 mm.

4. A long-wave infrared zoom lens as described in claim 1, characterized in that, During zooming, the maximum displacement of the second lens is 52.7 mm, and the maximum displacement of the third lens is 24 mm.

5. A long-wave infrared zoom lens as described in claim 4, characterized in that, During zooming, the interval between the first and second lenses ranges from 7.05622mm to 59.72631mm, the interval between the second and third lenses ranges from 5.98278mm to 82.87384mm, the interval between the third and fourth lenses ranges from 14.12166mm to 38.34177mm, and the interval between the fourth and fifth lenses is 35.42mm.

6. A long-wave infrared zoom lens as described in claim 1, characterized in that, The first to fifth lenses are all made of germanium.

7. A long-wave infrared zoom lens as described in claim 1, characterized in that, The image-side surface of the second lens, the object-side surface of the third lens, the object-side surface of the fourth lens, and the image-side surface of the fifth lens are aspherical and satisfy the aspherical formula: Where Z is the distance vector from the vertex of the aspherical surface at a height r along the optical axis; c = 1 / R; R is the paraxial curvature fitting radius of the mirror; k is the conic coefficient; A, B, C, D, and E are higher-order aspherical coefficients.

8. A long-wave infrared zoom lens as described in claim 1, characterized in that, The object side of the first lens is coated with a DLC film, and the image side of the first lens, as well as the object side and image side of the second to fifth lenses, are coated with anti-reflection films.

9. A long-wave infrared zoom lens as described in claim 1, characterized in that, The long-wave infrared zoom lens has an F-number of 1.2, a total optical system length of 193mm, a field of view range of 8°-40°, and is compatible with detectors with a resolution of 640×512 and a pixel size of 17μm.

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